Encapsulated Haemophilus influenzae type b strains are the major cause of bacterial meningitis and other invasive infections in young children. However, the non-encapsulated or non-typable H. influenzae (NTHi) are responsible for a wide range of human diseases including otitis media, epiglottitis, pneumonia, and tracheobronchitis. Vaccines based upon H. influenzae type b capsular polysaccharide conjugated to diphtheria toxoid (Berkowitz et al., 1987. Throughout this application, various references are referred to in parenthesis to more fully describe the state of the art to which this invention pertains. Full bibliographic information for each citation is found at the end of the specification, immediately preceding the claims. The disclosures of these references are hereby incorporated by reference into the present disclosure), tetanus toxoid (Classon et al., 1989 and U.S. Pat. No. 4,496,538), or Neisseria meningitidis outer membrane protein (Black et al., 1991) have been effective in reducing H. influenzae type b-induced meningitis, but not NTHi-induced disease (Bluestone, 1982).
Otitis media is the most common illness of early childhood with 60–70% of all children of less than 2 years of age experiencing between one and three ear infections. Chronic otitis media is responsible for hearing, speech and cognitive impairments in children. H. influenzae infections account for about 30% of the cases of acute otitis media and about 60% of chronic otitis media. In the United States alone, treatment of otitis media costs between 1 and 2 billion dollars per year for antibiotics and surgical procedures such as tonsillectomies, adenoidectomies and insertion of tympanostomy tubes. Furthermore, many of the causative organisms of otitis media are becoming resistant to antibiotic treatment. An effective prophylactic vaccine against otitis media is thus desirable. Non-typable strains of H. influenzae are also important pathogens responsible for pneumonia in the elderly and other individuals who are particularly susceptible to respiratory infections. There is thus a need for antigens from H. influenzae which are useful as components in immunogenic preparations that provide protection against the many serotypes of H. influenzae. 
Iron is an essential nutrient for the growth of many bacteria. Several human pathogens, such as H. influenzae, Branhamella catarrhalis, N. meningitidis, N. gonorrhoeae and non-pathogenic commensal Neisseria strains, can utilize human transferrin as an iron source (Schryvers, 1988; Schryvers and Lee, 1989; Mickelsen and Sparling, 1981). The bacterial transferrin receptor (TfR) is composed of two chains, Tbp1 and Tbp2. In strains of H. influenzae, the molecular weight of Tbp1 is approximately 100,000, whereas the molecular weight of Tbp2 is variable, ranging from 60,000 to 90,000, depending upon the strain (Schryvers and Gray-Owen, 1992; Holland et al., 1992). Expression of H. influenzae transferrin receptor is thought to be iron-and/or hemin-regulated (Morton et al., 1993) and a putative fur-binding site (Braun and Hantke, 1991) has been identified upstream of tbp2. This sequence is found in the promoter region of genes which are negatively regulated by iron, including N. meningitidis TfR (Legrain et al., 1993). The promoter is followed by the tbp2 and Tbp1 genes, an arrangement found in other bacterial TfR operons (Legrain et al, 1993; Wilton et al., 1993). Antibodies which block the access of the transferrin receptor to its iron source may prevent bacterial growth. In addition, antibodies against TfR that are opsonizing or bactericidal may also provide protection by alternative mechanisms. Thus, the transferrin receptor, fragments thereof, its constituent chains, or peptides derived therefrom are vaccine candidates to protect against H. influenzae disease. Mice immunized with N. meningitidis TfR proteins in Freund's adjuvant were protected from homologous challenge and the anti-TfR antisera were bactericidal and protective in a passive transfer assay (Danve et al., 1993). Pigs immunized with recombinant A. pleuropneumoniae Tbp2 were protected against homologous challenge but not heterologous challenge (Rossi-Campos et al., 1992). These data indicate the efficacy of TfR-based vaccines in protection from disease. It would be desirable to provide the sequence of the DNA molecule that encodes transferrin receptor and peptides corresponding to portions of the transferrin receptor and vectors containing such sequences for diagnosis, immunization and the generation of diagnostic and immunological reagents.
Poliovirus is an enterovirus, a genus of the family Picornaviridae. There are three distinct serotypes of the virus, and multiple strains within each serotype. Virulent strains are causative agents of paralytic poliomyelitis. Attenuated strains, which have reduced potential to cause paralytic disease, and inactivated virulent strains, are used as vaccines. Infection with the virus induces long-lasting, protective, mucosal immunity. Inoculation with inactivated poliovirus vaccines can also induce a mucosal immune response.
The structure of poliovirus is known, and is highly conserved among strains and serotypes. The structures of several other picornaviruses (viruses belonging to genera of the family Picornaviridae) have also been determined, and have been shown to be closely related to the structure of poliovirus. It is possible to express foreign epitopes on the capsid of polioviruses (Murdin et al, 1992) and this work has been extended to other picornaviruses. Epitopes which have been expressed are usually short, well defined, contiguous epitopes, and most have been expressed within poliovirus neutralisation antigenic site I (NAgI) or the equivalent site on other picornaviruses. This site includes the loop linking beta strands B and C (the BC loop) of poliovirus capsid protein VP1. The BC loop of VP1 is a surface-exposed loop of nine amino acids which can be replaced and extended with at least twenty-five heterologous amino acids (Murdin et al, 1991). Hybrid or chimeric polioviruses expressing transferrin receptor epitopes, which grow to a high titre and are immunogenic, would be useful as vaccines and as tools for the generation of immunological reagents.